In off-machine coating machines, a continuous unwind stand is used in which the new machine reel to be introduced in the unwind stand is joined at full speed with the tail of the machine reel that is being emptied. In modem high-speed coating machines, the splicing method is, in principle, the same irrespective of the manufacturer of the machine. At the end of the web on the new machine reel, in advance, a splice is prepared by means of double-sided adhesive tape, which splice is attached to the reel face by means of pieces of adhesive tape. The circumferential speed of the new machine reel is raised to a level equal to the running speed of the machine, after which the web of the machine reel that is being emptied is pressed into contact with said splice, for example, by means of a roll or brush. The old web is cut off by means of a blade from above the splice.
The splicing in an unwind stand has become problematic at the current running speeds (1200 . . . 1600 metres per minute). Out of this reason, the running speed of the splicing machine is often lowered for the time of splicing. At a high speed, a vacuum is formed in the what is called splicing gap placed between the machine reel and the splicing roll brought to the vicinity of said reel, which vacuum can be pulsating if the new machine reel is non-circular. The vacuum tends to attract the old web partly into contact with the splice even before splicing, and the vacuum also causes fluttering of the old web. Further, the vacuum tends to separate the tape splice from the face of the new machine reel, in which case the new machine reel is opened before splicing. In order that the running of the web should be controlled, at the splicing roll a bend is required, which again requires stretching of the web when the splicing roll is hit quickly onto the face of the new machine reel. Attempts are made to keep the tension peak caused by the hitting of the roll in splicing low by using a little splicing gap (8 . . . 12 mm), which produces an intensive vacuum effect. Even the bending angle that is used currently causes a problematic tension peak in the web. At higher running speeds an even larger bending angle would be required.
In the FI Patent Application No. 942869, a splicing device for a continuous unwind stand is described, by whose means the new machine reel brought to the unwind stand is connected at full speed with the web of the machine reel that is being emptied. The splicing device comprises a splicing roll, by whose means the web of the machine reel that is being emptied is pressed into contact with the splice placed on the new machine reel, and at least one second roll. The splicing roll and said second roll are attached to a lever device, which is mounted by means of an articulation point placed between the shafts of said rolls, so that the run of the web before splicing and the run of the web during splicing are such that the length of the web during splicing and when said rolls are in their basic positions is substantially equal.
At high running speeds and in particular with heavy paper grades, in flying splicing, a problem has been the control of the cut-off tail of the old machine reel. After the splicing, attempts are made to stop the reel spool that is being emptied quickly. Paper must not be unwound to such an extent that it cannot be controlled by means of blowing of air. The tail of the cut-off web and any paper chips must be kept away from the splicing nip. If the cut-off tail ends up onto the web, it causes a web break. Also smaller paper chips can cause a web break if chips are carried along with the web, for example, to a coating station. Even if a paper chip separated from the tail did not cause a web break, it, however, causes cleaning work after splicing.
In order to solve this problem, some manufacturers have constructed inverted unwind stands, in which the geometry has been turned upside down. It is the purpose of the inverted geometry that, after the splicing, the cut-off tail and any paper chips that are separated fall away from the web by the effect of gravity. At higher speeds (higher than 1400 metres per minute), even this is not of any use, because the air flows present on the faces of the departing web and of the large machine reel that is being unwound are so intensive that the direction of the gravity remains insignificant.
Traditionally, for the control of the cut-off web, blowings have been employed, by whose means attempts are made to guide the tail around the reel spool to be slowed down and to prevent access of the tail and of separated chips to the departing web. Attempts are made to stop the reel spool that is being emptied by means of mechanical brakes quickly. This requires high capacity from the brakes and, thereby, causes rapid wear of the brakes. The brake pads of the brakes must be renewed frequently. At present, a typical stopping time of about 4 seconds is in use. With the present-day technology, a target time for stopping the reel would be about 1.5 seconds, irrespective of the speed or of the size of the reel spool. In large machines, such a time would involve a braking capacity of up to 10 MW. At present, there are production machines in which the brake devices must be replaced even at intervals of 2 months, which means, among other things, a considerable expense in terms of money.
In very narrow unwind stands (width about 1 metre) of the revolver type, which are used at printing machines, occasionally, a double-sided tape is used on an intermediate roll placed before the cut-off roll, which tape captures the cut-off tail around it. After splicing, the intermediate roll is unwound and cleaned manually. The tape is difficult to remove from the intermediate roll, but this is necessary after each splicing cycle. In large high-speed unwind stands (roll diameter φ=1000 mm, length 8000 mm) such fitting of tapes and manual cleaning are directly impossible, because there is not time enough for the necessary manual cleaning between splicing cycles.
In machines for coating of a paper web, first a layer of paste is applied onto the paper web by means of an applicator device, and after that the coating is smoothed by means of a doctor blade against the same backup roll.
In the Finnish Patent No. 93,665, a method and an equipment are described for coating of a paper web, wherein the application and the smoothing proper are arranged so that each process has a backup face of its own. Of the backup faces, at least the latter one drives the web or moves at least substantially at the same speed as the web. By means of independent backup faces, it is possible to control the tension of the web placed between the holding points and to prevent detrimental bag formation in, or slackening of, the web between the holding points.
In the Finnish Patent No. 94,883, a method and an equipment are described for double-sided coating of a thin printing-paper web that contains mechanical pulp. In this prior-art method, the first side of the web is coated by means of a first coating station, the first coating layer is dried at least partly by means of a drying equipment, and the second side of the web is coated, after drying of the first side, by means of a second coating station, and the second coating layer is dried at least partly by means of a second drying equipment. The first and the second coating layer are formed by applying the necessary amount of coating agent onto the face of a film roll, from which the coating agent is transferred onto the web in a nip between a backup roll and the film roll. The drying equipment can consist of infrared dryer units and of drying cylinders.
As is well known, in paper web coating machines, air dryers, i.e. airborne web dryers, have also been employed.
Clearing up of web breaks taking place in a coating machine requires an abundance of time from the operating team, and losses in production arise. The clearing up of a web break mainly consists of the following steps of work:                Clearing of paper chips from the machine, in particular from between the airborne web dryers.        Washing of the coating stations.        
In order that winding of the web around the backup rolls could be avoided, which winding might damage the rubber-coated backup rolls, the coating machine is typically provided with a web break monitoring system and with cutter blades before each coating station. When it operates correctly, this system protects the backup rolls but may, otherwise, cause even more paper chips to be cleared from the machine than without web break monitoring. This comes from the fact that the web tension goes down to zero after the cutter blade has cut off the web, in which connection the free tail moves readily to the sides, is cut off when it strikes against the frames, and remains in its place, e.g., inside the airborne web dryers. Corresponding situations in which the control of the web is lost, in the event of a web break or when the web is cut off intentionally, also occur, among other things, in intermediate winders, slitter-winders, and even in paper machines in some cases.